1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus capable of performing detection of blood flow perfusion and quantitative evaluation of the perfusion by using an ultrasonic contrast agent.
2. Description of the Related Art
An ultrasonic diagnostic apparatus can non-invasively obtain a tomogram image of a soft tissue in a living body from a body surface by an ultrasonic pulse reflection method, and has features that it is smaller in size and inexpensive, capable of real-time display, has high safety without exposure to, e.g., X rays and capable of blood flow imaging, as compared with any other diagnostic apparatus such as an X-ray diagnostic apparatus, an X-ray CT apparatus, an MRI diagnostic apparatus or a nuclear medicine diagnostic apparatus. The ultrasonic diagnostic apparatus is currently commonly used for hearts, abdominal parts, a urinary organs, and obstetrics and gynecology because of its conveniences mentioned above.
As one of radiography methods of the ultrasonic image diagnostic apparatus, there is a technique called contrast echo. This intensifies the ultrasonic scattering echo by injecting an ultrasonic contrast agent consisting of, e.g., micro-bubbles in a blood vessel of a patient. For example, in an examination of a heart or an abdominal organ, its purpose is to inject an ultrasonic contrast agent from a venation and intensify a blood flow signal in order to evaluate a blood flow dynamic state. In particular, in case of injecting the ultrasonic contrast agent into the venation, the invasiveness is low. Therefore, since the burden on a patient is lightened, the diagnosis based on this method of evaluating the blood flow dynamic state is getting popular.
Further, in recent years, an ultrasonic scanning sequence called intermittent transmission which makes use of the ultrasonic contrast agent has been developed and is outstanding successful in the clinical or study field. This intermittent transmission is a scanning sequence which waits until the ultrasonic contrast agent is sufficiently filled in a region of interest and then performs transmission of the ultrasonic waves. Furthermore, it destructs and dissolves the micro-bubbles at a blast in order to obtain the high signal intensity. Generally, in this intermittent transmission, it is ideal that one-frame scanning is carried out in accordance with each intermittent interval and the micro-bubbles filled in the cross section of a target are diminished and dissolved at a blast, thereby observing an area where the micro-bubbles have existed.
However, the micro-bubbles may not be diminished and dissolved sufficiently in one frame scanning depending on types or concentrations of the contrast agent or a transmission acoustic field in some cases. Moreover, when the concentration of the contrast agent is too high or the transmission acoustic pressure is too low, attenuation of the acoustic pressure by the micro-bubbles becomes large, and the intensity of a reflection signal at a deep part can not be satisfactorily obtained. Alternatively, even if the sufficient signal intensity is obtained, the S/N ratio may be very poor, a phenomenon which glooms an image, which is so-called shadowing, may occur. In such cases, since the distribution state of the micro-bubbles in the scanning cross section at a deep position is not perceived and a ratio of destruction of the micro-bubbles varies, appropriate quantitative evaluation can not be performed. In addition, if the micro-bubbles in the scanning cross section can not be once completely diminished, dynamic observation of the blood flow dynamic state also becomes difficult.
As means for avoiding this problem, there is a technique disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 9-164138. This technique makes judgment upon at which depth information of bubbles of a patient is obtained based on an absolute value of a difference between frames calculated by using data acquired by transmission of strong ultrasonic waves and data acquired by transmission of weak ultrasonic waves. Additionally, based on this judgment, transmission and reception of ultrasonic waves in which a focusing point is automatically shifted from a shallow part to a deep part are repeated, and an obtained absolute value image is integrated and displayed.
In this technique, however, a number of times of transmission and reception of ultrasonic waves is usually twofold of a number of regular frames, and transmission/reception control or judging means may be possibly complicated. Further, since a number of frames is large, it takes time to collect data of all frames. Thus, a difference in time between an image of the frame collected at first and the frame collected at last becomes large, and the displacement of an image due to movement becomes prominent when creating an image of a moving target, thereby deteriorating the picture quality.
Meanwhile, for the purpose of completely destructing and dissolving the micro-bubbles, there is a technique which performs frame scanning for imaging several times after intermittence, which is so-called multi-shot. According to this multi-shot, a number of times of multi-shot to be required differ depending on types or concentrations of contrast agent or a transmission acoustic field. However, selecting appropriate conditions can makes the micro-bubbles in the scanning cross section diminished and dissolved at a high ratio by.
Incidentally, a point of notice is that multi-shot can insistently completely destruct the micro-bubbles contained in the cross section of an observation target and rest to an initial state with no micro-bubbles and it is not means for extracting information of the diminished micro-bubbles. That is, even if all the micro-bubbles are diminished by multi-shot, a frame image corresponding to each shot can not independently provide information of all the micro-bubbles in the cross section as an observation target. In this case, even if any frame is selected, an image whose brightness is irregular in the depth direction is generated, the correct distribution of the contrast agent can not be obtained. Also, in quantification measurement using the contrast agent, correct evaluation can not be obtained unless an evaluation area can be appropriately selected.
It is an object of the present invention to provide means capable of accurately and effectively performing detection of blood flow perfusion and its quantitative evaluation even if a quantity of a contrast agent to be injected is large or a concentration of the same is high.
To achieve this aim, the present invention takes the following configurations.
According to a first aspect of the present invention, there is provided an ultrasonic diagnostic apparatus comprising: a transmission/reception device which transmits for a plurality of times ultrasonic waves having an intensity capable of destructing a contrast agent to one scanning plane of an object to which the contrast agent has been injected and receives a reflected wave group from the object; a data generator which generates a plurality of accumulative addition data having different time phases based on at least one of a plurality of reflected waves constituting a plurality of continuous frames in the reflected wave group and generates subtraction data from a reflected wave received from the object with a predetermined timing; and an image information generator which generates calculated data having an operation value to which a plurality of the accumulative addition data has been accumulatively added and from which the subtraction data has been subtracted, and generates ultrasonic wave image information concerning the scanning plane based on the calculated data.
According to a second aspect of the present invention, there is provided an ultrasonic diagnostic apparatus comprising: a transmission/reception device which transmits for a plurality of number of times ultrasonic waves having an intensity capable of destructing a contrast agent to one scanning plane of an object to which the contrast agent has been injected, and receives a reflected wave group from the object; a data generator which generates a plurality of accumulative addition data having respective time phases based on at least one of a plurality of reflected waves composing a plurality of continuous frames in the reflected wave group, and generates subtraction data from a reflected wave received from the object with a predetermined timing; a memory which stores therein a plurality of the accumulative addition data; and an image information generator which generates calculated data obtained by subtracting the subtraction data from each of the accumulative addition data stored in the memory, and generates ultrasonic image information concerning the scanning plane based on the calculated data.
According to a third aspect of the present invention, there is provided an ultrasonic diagnostic apparatus control method comprising: transmitting for a plurality of number of times ultrasonic waves having an intensity capable of destructing a contrast agent to one scanning plane of an object to which the contrast agent has been injected; receiving a reflected wave group from the object; generating a plurality of accumulative addition data having respective time phases based on at least one of a plurality of reflected waves composing a plurality of continuous frames in the reflected wave group; generating subtraction data from a reflected wave received from the object with a predetermined timing; generating calculated data having an operation value to which a plurality of the accumulative addition data have been added and from which the subtraction data has been subtracted; and generating ultrasonic image information concerning the scanning plane based on the calculated data.
According to a fourth aspect of the present invention, there is provided an ultrasonic diagnostic apparatus control method comprising: transmitting for a plurality of number of times ultrasonic waves having an intensity capable of destructing a contrast agent to one scanning plane of an object to which the contrast agent has been injected; receiving a reflected wave group from the object; generating a plurality of the accumulative addition data having different time phases based on at least one of a plurality of reflected waves composing a plurality of continuous frames in the reflected wave group; generating subtraction data from a reflected wave received from the object with a predetermined timing; generating calculated data obtained by subtracting the subtraction data from the each of accumulative addition data; and generating ultrasonic image information concerning the scanning plane based on the calculated data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.